modpost: rename alias symbol for MODULE_DEVICE_TABLE()

This commit renames the alias symbol, __mod_<type>__<name>_device_table
to __mod_device_table__<type>__<name>.

This change simplifies the code slightly, as there is no longer a need
to check both the prefix and suffix.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>